January 12, 2006 2 Few Points Few Points Few Points ß Movie “Powers of Ten” at the end of the lecture (if time) ß No class on Monday: MLK Day ß Lisa Lapidus takes over section 001 on Tuesday ß Homework • First set opened • Due by Wednesday 23:59 ß Clicker Quizzes (trials) begin next week

January 12, 2006 4 Scientific Notation Scientific Notation Scientific Notation ß Physical quantities consist of a number that specifies its magnitude AND its unit • Example: this lecture lasts 50 minutes (number) (unit) ß For very large or very small numbers, we use scientific notation number = mantissa • 10 (exponent) • Example: 3.2·10-12 (or 3.2x10-12 ) • Product easy: (4.8x10-17 )x(7.21x10 7 )=34.6x10-10 =3.46x10-9 • You must enter number in scientific notation into the LON-CAPA homework system as 3.2e-12 (or 3.2E-12)

January 12, 2006 5 Significant Figures Significant Figures Significant Figures ß Two statements: • The population of the USA is 294,109,799 • The population of the USA is 294,000,000=2.94·10 8 • First statement implies precision that is simply not warranted • Second statement claims that the population is somewhere between 293M and 295M. This is justified! ß General Rule: • The number of digits we write down in a number specifies the precision with which we claim to know that number. US Census Bureau August 2004 US Census Bureau August 2004

This
preview
has intentionally blurred sections.
Sign up to view the full version.